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Friday, August 23, 2019

Is Western Washington Really in Severe Drought?

For society to make good decisions on environmental matters, decision makers inside and outside of government require accurate and realistic guidance. For that reason, I am a bit worried that there is a problem with a frequently cited source of information about drought across the U.S.: the U.S. Drought Monitor website.

The latest release of this information suggests that Washington State is one of the most drought-affected locations of the U.S., with much of western Washington in severe drought.

Below is an expanded version of the graphic for just Washington State. Severe drought along the coast, much of SW Washington and the western slopes of the northern WA Cascades. Moderate drought over more than half the state.

Now is it reasonable to suggest that much of our state is in moderate to severe drought? Severe drought sounds quite scary to me and one would expect extremely serious problems as a result.

Let us begin by looking at the difference from normal of precipitation for the summer so far. Most of the Northwest has been near normal, including the supposed "severe drought" area.

Current streamflow? Most sites are near normal (green colors). A large number are above normal (cyan and dark blue), a similar number are below normal (orange and red).

Wildfires are below normal across the State this year, as is smoke.

What about water resources? All the major urban areas have plenty of water, without any drought restrictions. Seattle's reservoirs are slightly below normal, with no water issues (see below).

The only water resource issues are on the Olympic Peninsula, where Port Angeles and few small water districts are asking for voluntary reductions in water usage. I could find no impacts on agriculture or any other industry due to the "drought."

The origin of the drought declaration is from the relatively dry winter we had last year, something illustrated by the figure below, which shows the difference from normal of the total precipitation since October 1, 2018. Southeast Washington was wetter than normal, but the coastal zone and the western Cascade slopes were drier than normal. But having a location that normally gets 100 inches a year, now receive 80 inches, is a far cry from a severe drought and the impacts are very modest at best. And a dry winter was supplanted by a normal summer even in those parts.

Another way to appreciate this year's precipitation situation is to view the cumulative precipitation over the past year For Seattle, we ended up with about 80% of normal precipitation (see below, normal is cyan, observed is purple)

And the situation is similar at Quillayute, on the northern Olympic Peninsula coast.

80% of normal precipitation does not represent an extreme drought and has occurred many times during the past 50 years.

My own opinion is that the term severe drought is not appropriate for the kind of situation observed in western Washington this summer--- one with few impacts and not that unusual. Using such strong terminology makes it harder to get folks to react when a real severe drought occurs and doesn't accurately communicate the actual threat level. And some politicians use such overly exuberant language to push their agendas.

This is the kind of year that "abnormally dry" might be appropriate and the "D word" might not be the best choice. Extreme drought seems over the top.

23 comments:

Thanks for pointing this out once again Cliff, this is something that has always bothered me! In past years we have actually been above normal precip and yet it still shows we're in a drought. Being hyperbolic with climate or the weather just turns a lot of people off from the subject and creates a real disservice to the importance of it.

Can we also look at river flows. I live in Skagit County and river levels are much lower for this time of year. The farmers of Skagit County are irrigating in ways that I haven't seen. They are now taking extra water from Anacortes water rights. We always pick and chose but on the ground we see things differently. I don't get to fish again this year on the Skagit. That is what matters to me.

Here in Union, Southern Hood Canal, we recently had a sudden wildfire that would have taken out a good section of our town had it not been for mobilization ot hundreds of first responders and air drops of water. Trees were crowning and we had to evacuate our area. Never experienced this in our 40 plus years here. Been getting bits of rain at times but is very dry down deep.

As a farmer I am struggling with persistently low soil moisture. My plants are dry dry dry, from roots to leaves, even with supplemental watering, even with a few days of rain. Leaves are dry and seem challenged by lack of moisture in the air too. Official drought or not, growing conditions have been much tougher than usual.

I agree with you that the terminology is misleading. That said, it is my observation on South Whidbey that our forests are extremely dry, and are suffering from multiple dry growing seasons in a row. We're seeing increased mortality in all of the major, dominant tree species. Sure we've had some unexpected rain this month, which has helped and probably saved countless trees. The lower temperatures have also been helpful. However, this amount of rain has not made up the deficit.

Reservoir levels and stream flows are only part of the hydrologic picture. I'm interested in learning more about ground water levels during dry years, particularly the health of island aquifers like our water source on Whidbey.

Thanks for laying this out! Just an anecdotal bit, and not directly correlated to drought data, but my large yard is still deeply green. I don't water it, and usually this late in the summer it is all brown.

The drought index is primarily about growing conditions. That is soil moisture and vegetation conditions, not necessarily water resources (especially reservoirs). I agree that the subjective labels of the drought monitor seem to be poorly descriptive. That doesn't mean that conditions in western Washington are not unusually dry. As other commentators have pointed out: they are.

Perhaps there will be more support for this currently experiment index: the evaporative demand drought index. This index is a more quantitative way of measuring drought as the relationship between two variables: precipitation and water use of vegetative community. It also does away with "extreme" and "exceptional" descriptors.

The current index shows an anomaly for western Washington, especially southwest Washington: https://www.esrl.noaa.gov/psd/eddi/#current_conditions In short, we can take this mean that there is an evaporative deficit when compared to historical conditions. This isn't just a function of precipitation, as they point out in the user guide (https://www.esrl.noaa.gov/psd/eddi/pdf/EDDI_UserGuide_v1.0.pdf) drought can emerge even when precipitation is near-normal if evaporative demand is much higher than average. Evaporative demand is a function of temperature, humidity, wind speed and solar radiation aggregated overtime.

The index is unusually well documented, so kudos to the team that put this together. And there are probably things to quibble about (like the use of 0.5 m reference crop applied to what are primarily forest terrain).

Showing the USGS hydrographs from Thursday is a bit misleading, as a number of rivers on the Olympic Peninsula had just risen in response to a rain event. They are now dropping again already. A few days prior, many of those rivers were near all-time record low flows.

For anyone who wants a more detailed description of how drought is defined and measured over different timescales and the different types of models involved, this is helpful: "https://www.ncdc.noaa.gov/temp-and-precip/drought/recovery/".

I think some of the dryness issues date back to last spring and summer and also this spring which was dry. Many areas saw below normal winter rainfall too due to abnormal patterns that saw some areas get copious amounts of rainfall and others stuck under a near constant rain shadow due to a persistent flow. Thankfully the summer has been on the wetter side and up north in BC its been very wet, there is no talk of drought that's for sure and some rivers that flow through Washington, their upper reaches are in BC like the Skagit and the Columbia so these rivers should be in tip top shape.

Unfortunately not true for the part of Skagit River flowing through Southwest Skagit County. That's why Skagit PUD has just allowed emergency withdrawals to enable farmers to bring crops to haven't. Article in goskagit.com

Yes. Dryness has been on going for a few years now. The Skagit River has 3 dams upstream in the US which use the water to supply power to Seattle. Also holds water for later use in the year. Our snow pack this year was half of normal and therefore would provide much less river water when melting in the summer.

I agree that “severe” is over the top. I'm familiar with the drought classifications, definitions, and methodology (and state law regarding declarations). Unfortunately this isn't the first year that the official maps don't reflect reality. This isn’t our first “wet drought.” Drought requires "water shortage" AND "hardship," and this year there's little-to-no evidence that real, widespread drought materialized as predicted.

I love our Mediterranean climate with its natural, seasonal dry period. We’ve had more summer rain this year than last year (2018), and last summer there was more rain than the year before (2017). Most parts of Whatcom County (WRIA 1) are not experiencing even "D0 - Abnormally Dry" conditions much less "D2 - Severe Drought." It keeps raining, grass keeps growing, and we're still mowing (that's very odd for August). I’ve inquired, and WA Ecology has "no plans at this time" to end the drought declaration (slated to last a full year). No matter what conditions are, drought grants have been feverishly applied-for. It's quite possible that we may be "raising a glass to drought" on Festivus. Nuts.

Scott 8 and others: I understand how statistics led to "predictions," but end of the day it's reality that matters. If "drought monitor" classifications do not reflect actual conditions, it would seem that the Drought Monitor maps are wrong. "D2-Severe Drought: Crop or pasture loss likely, Water shortages common, Water restrictions imposed." We do have our natural, seasonal dry period that shouldn't be conflated to "drought" (most particularly when it's raining). Just my opinion.

I see no problem with NOAA's drought index Abnormally dry in our area (western WA). Remember this designation may trigger other outcomes than just a pleasant day in your backyard or your local activities.

I pay attention to this site, and I agree with the drought designation. It affects our plans for trying to maintain a very small farm with just a couple of cows. I need to plan to keep them fed (with hay when pastures dry out and through the winter) and watered ~ with a well tapping a diminishing aquifer) We try to protect/shade soils on our place. Moisture disappears fast when exposed to the dry air and sun.

We see droughty conditions all around us: trees shedding leaves & branches (a survival technique when they can't take up enough water through their roots, grasses dying when their roots can't find water, even normally wet areas are drying out, stream flows are now just trickles (or totally gone), fires constantly breaking out in dry vegetation all around us.

The Weather Forums DOT com one of the members say you have an article about the warmth on the eastern Pacific being nudged westward with height rises over the NE Pacific due to ENSO being neutral among other things but I can't find it.

Laughable that the word drought would be used in Washington. The politicizing of weather to advance Socialism, that's what passes for much of science today. Progressives are fond of the adage: "Never let a crisis go to waste."

And if you don't have a crisis handy, you invent one. Severe Drought? BS.